The mobile Internet industry and the Internet of Things industry have developed rapidly, and an Internet of Things network device is low-cost, easy to deploy, and maintenance-free. In an enterprise market, main communication requirements of enterprise Internet of Things are a small amount of data and mass connections. Compared with a licensed spectrum of an operator, an unlicensed spectrum, especially a frequency band of Sub GHz, can effectively reduce network costs. Therefore, a narrowband communications system based on the unlicensed spectrum can meet the requirements.
Each region in each country has corresponding regulations on the unlicensed spectrum, so as to prevent all devices from irregularly and limitlessly sending data on the unlicensed spectrum. Before accessing a network, a device needs to be certified by regulations of each country. In other words, any device may not monitor a channel before sending data, but needs to meet a specific sending duty cycle; that is, total sending time of the device cannot exceed a threshold within a specific time.
In order to meet a requirement of regulations on the duty cycle, two technical means are commonly used in the unlicensed frequency band: one is listen before talk (LBT), that is, any device needs to monitor the channel before sending data; and the other is frequency hopping, that is, after sending the data on a channel for a period of time, the device switches to another frequency band to use another channel. Frequency hopping in a Bluetooth technology is used as an example. Bluetooth is a short-range wireless communications technology operating on an ISM frequency band of 2.4 GHz (2.40 to 2.48 GHz), and can form a small wireless personal access network (PAN). Bluetooth uses a series of unique measures such as Adaptive Frequency Hopping (AFH), LBT (Listen Before Talk), and power control to overcome interference and avoid conflicts.
However, Bluetooth uses a time division multiple access technology, and a central device cannot communicate with a plurality of secondary devices at a same time point, and therefore a Bluetooth primary device cannot connect to many secondary devices at a same time point. Consequently, a requirement of the Internet of Things for mass connections cannot be met.